This, however, came after a demonstrator reportedly snatched one of the Palestinian flags from the truck and stomped on it.
"I saw my flag on the ground," Hany Reai, a Palestinian supporter, told CNN affiliate KCAL, "and I saw a man step on it. I'm not here to fight. I just need my flag, and I ran to take it."
But one witness told the Los Angeles Times the clashes were deliberately provoked by the men in the truck with Palestinian flags.
"They were looking for a fight," Judy Friedman told the newspaper. They were "taunting and threatening" people, thrusting their sticks toward demonstrators on the sidewalk.
A video purportedly recorded by a student at the protest and published on the website of the Jewish Journal of Greater Los Angeles shows insults flying in both directions.
The Federal Protective Service called for an ambulance to treat a woman allegedly hurt by the men, who were later picked up and booked on suspicion of assault with a deadly weapon. They've since been released on bail, deny the charges and say they were "falsely arrested," the Los Angeles Times reported.
And as if this ruckus wasn't already heated enough, as the pickup drove off, an officer with FPS -- who was trying to stop the men from leaving -- fired his weapon. No one was hurt. That officer has been placed on paid administrative leave while the incident is investigated, officials said.
From clicks to clashes
As the rocket attacks from Gaza and Israeli airstrikes show no signs of slowing, hostilities are flaring online as much as they are in the streets.
Over the weekend, #HitlerWasRight trended on Twitter, part of what the ADL described as an "online outpouring of anti-Semitism."
The group said Wednesday that a surge in Hitler-related hashtags might be fueling hatred at rallies as well.
Anti-Arab statements have also run rampant online.
A now-discontinued Facebook page called "The People of Israel Demand Vengance," racked up thousands of likes earlier this month, the Times of Israel reported.
On the page, according to the newspaper, users posted photos with captions like "death to the whole Arab nation" and "Hating Arabs is not racism; it's morality."